The present invention relates to a solid-state imaging apparatus having a plurality of photoelectric converting elements each forming an imaging pixel and having a structure for reading a signal charge accumulated in each of the photoelectric converting elements on a dot-sequential basis using a plurality of transistors, and a driving method of the solid-state imaging apparatus.
Conventionally proposed as a solid-state imaging apparatus of this type is an X-Y addressing type image sensor that is provided for each unit pixel with a photodiode for photoelectric conversion and a total of five MOS transistors: a gate for reading a signal charge accumulated in the photodiode; a reading selection gate; an amplifying gate; a reset gate; and a horizontal selection gate, and which is capable of reading the signal charge in each unit pixel on a dot-sequential basis (see Japanese Patent Laid-Open No. 2001-24952 and Japanese Patent Laid-Open No. 2001-24946, for example).
Specifically, in the image sensor, a signal charge corresponding to an amount of light received by the photodiode is read by the reading transistor and transferred to an FD (floating diffusion) part connected to a gate of the amplifying transistor. The signal charge is amplified by the amplifying transistor and thus converted into a current signal corresponding to potential of the FD.
Then, the output of the amplifying transistor is outputted by the horizontal selection transistor in predetermined timing, and sent to a signal processing circuit provided outside the imaging area.
Operation of the reading transistor is selectively controlled by the reading selection transistor, whereby a pixel from which to read a signal charge is selected.
The reset transistor resets the signal charge of the FD to a power supply level.
An image sensor having a pixel structure formed by five such transistors will be referred to as a solid-state imaging apparatus of a dot-sequential reading 5-Tr type.
However, in the related-art solid-state imaging apparatus as described above, when depletion occurs in a lower layer of a gate region of the reading transistor for transferring the signal charge to the FD, leakage current is correspondingly increased and grain-like noise occurs on the screen.